Welcome, please format your post accordingly, currently it's unnecessarily difficult to follow. How do I post a question effectively?. Also please post the appropriate sections of tnsnames.ora and listener.ora. Perhaps you're not setting your ORACLE_HOME environment variable properly. A quick test is to set this in your perl script before you try to connect. The DBD::Oracle documentation mentions this.

In reply to Re: ORA-12154: TNS:could not resolve the connect identifier specified (DBD ERROR: OCIServerAttach) by marto
in thread ORA-12154: TNS:could not resolve the connect identifier specified (DBD ERROR: OCIServerAttach) by rajesh_perl

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